The invention relates to a delivery for a machine processing flat printing materials, in particular a sheet-processing printing machine, having a sheet guide surface, suction openings opening into the sheet guide surface, a suction chamber communicating with the suction openings, and a sheet conveyor for gripping a respective sheet at an edge thereof leading in a conveying direction and dragging it over the sheet guide surface, and also to a machine for processing flat printing materials, which is equipped with the delivery.
The aforementioned delivery drags sheets printed on one side thereof over the sheet guide surface in such a way that the unprinted side of the sheets (in the case of recto or Single-side printing) is attracted by suction in a direction towards the sheet guide surface. A delivery of this type is disclosed, for example, by the published German Patent Document DE 34 11 029 C2 and is representative of the prior art, to the extent that air nozzles provided therein, which open into the sheet guide surface, communicate at least to some extent with a vacuum generator and are directly connected to ducts which, in the case of recto printing, are in particular connected to the suction side of fans or blowers. The objective which is pursued with this device is to achieve quiet running of the sheets over the sheet guide surface. To this end, a relatively high output from the respective fan or blower is required, because in no operating state are all the air nozzles covered by sheets and, therefore, unwanted air is sucked through some of these air nozzles, which results in a condition wherein, even with a high output from the fans, only low suction forces act upon the sheets dragged over the sheet guide surface, so that quiet running of the sheets can be achieved only with an extremely high outlay of power.
It is accordingly an object of the invention to configure the delivery referred to at the introduction hereto in such a manner that a quiet or smooth sheet run is achieved with the lowest possible outlay of power for the generation of suction forces which are required to guide the sheets along the sheet guide surface.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a delivery for a machine for processing flat printing materials, comprising a sheet guide surface with suction openings opening into the sheet guide surface, a suction chamber communicating with the suction openings, and a sheet conveyor for gripping a respective sheet at an edge thereof extending in a sheet-conveying direction and for dragging the respective sheet over the sheet guide surface, the suction chamber being formed as a throttling duct.
In accordance with another feature of the invention, the suction openings are subdivided into groups, each group of a plurality of groups selected from the groups of suction opening being assigned to a respective throttling duct exclusively.
In accordance with a further feature of the invention, a respective throttling duct assigned to the groups of suction openings has an extent in the conveying direction which is at most equal to a corresponding extent of smallest possible sheets which can be processed.
In accordance with an added feature of the invention, a respective throttling duct has a first suction connection at an end thereof located upline with respect to the sheet-conveying direction, and has a second suction connection at an end thereof located downline from the upline end thereof.
In accordance with another aspect of the invention, there is provided a machine for processing flat printing materials, including a delivery, comprising a sheet guide surface with suction openings opening into the sheet guide surface, a suction chamber communicating with the suction openings, and a sheet conveyor for gripping a respective sheet at an edge thereof extending in a sheet-conveying direction and for dragging the respective sheet over the sheet guide surface, the suction chamber being formed as a throttling duct.
In accordance with an additional feature of the invention, the machine is a sheet-processing printing machine.
In accordance with a concomitant aspect of the invention, there is provided a sheet-processing printing machine including a delivery, comprising a sheet guide surface with suction openings opening into the sheet guide surface, a suction chamber communicating with the suction openings, and a sheet conveyor for gripping a respective sheet at an edge thereof extending in a sheet-conveying direction and for dragging the respective sheet over the sheet guide surface, the suction chamber being formed as a throttling duct.
A result of the improved construction, compared with the heretofore known delivery according to the aforementioned patent document, is a lower drop in the vacuum in the suction chamber which, according to the invention, is constructed as a throttling channel and connected directly to the suction openings, as compared with the drop in vacuum in the corresponding suction chamber of the aforementioned heretofore known delivery when some of the suction openings, without a sheet covering the latter instantaneously, produce a direct connection between the suction chamber and the atmosphere. This increases the suction force exerted on the sheets by a vacuum generator as compared with the suction force exerted by a vacuum generator having an identical output in the heretofore known construction.
According to a development of the invention, the suction openings are subdivided into groups and each group is associated with its own throttling duct. In addition to further advantages explained hereinafter, this also provides production advantages as compared with an implementation of a single throttling duct underneath a guide plate provided with the suction openings.
Subdividing the suction openings into groups and allocating and configuring respective throttling ducts can be carried out in various ways.
In a preferred configuration, subdividing the suction openings and allocating throttling ducts is implemented in such a way that a respective throttling duct associated with one of the groups of suction openings has an extent in the conveying direction which is at most equal to the corresponding extent of smallest possible sheets which can be processed.
In addition, one advantageous refinement provides for a respective throttling duct to be provided with a first suction connection at an end of the throttling duct disposed upline with respect to the conveying direction, and to be provided with a second suction connection at an end of the throttling duct disposed downline from the upline throttling-duct end.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a delivery for a machine processing flat printing materials, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: